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Plasma generator and method of generating plasma using the same meetings

Foreign code F120006826
Posted date Aug 9, 2012
Country United States of America
Application number 22475007
Gazette No. 20090260972
Gazette No. 8216433
Date of filing Feb 17, 2007
Gazette Date Oct 22, 2009
Gazette Date Jul 10, 2012
International application number JP2007052893
International publication number WO2007105411
Date of international filing Feb 17, 2007
Date of international publication Sep 20, 2007
Priority data
  • P2006-061673 (Mar 7, 2006) JP
  • 2007WO-JP52893 (Feb 17, 2007) WO
Title Plasma generator and method of generating plasma using the same meetings
Abstract (US8216433)
A plasma generator in which the variation of the impedance in the cavity before and after plasma is ignited is less and hardly affected by the shape of the cavity, and the ignitability of the plasma is improved and a method of generating plasma using the plasma generator are provided.
The plasma generator comprises a nonconductive gas flow pipe (1) for introducing a gas (9) for generating plasma and discharging it into the atmosphere and a conductive antenna pipe (2) surrounding the gas flow pipe.
A microwave (7) is applied to the antenna pipe to change the gas in the gas flow pipe into plasma.
The plasma generator is characterized in that a slit (3) with a predetermined length is formed in the antenna pipe (2) along the axial direction of the gas flow pipe.
Preferably, the plasma generator is characterized in that the length of the slit is an integral multiple of the half-wave length of the applied microwave.
Scope of claims [claim1]
1. A plasma generator, comprising a non-conductive gas flow pipe through which a gas for generating plasma is introduced and discharged into air, and
a conductive antenna pipe surrounding the gas flow pipe, wherein
the plasma generator irradiates the antenna pipe with microwaves so that the gas in the gas flow pipe is converted to plasma,
the plasma generator comprises a waveguide that has a rectangular cross-sectional shape, and that propagates microwaves generated by a microwave generator,
the antenna pipe is arranged at a part of the waveguide, and penetrates through facing surfaces forming the waveguide, and
a slit of a predetermined length is formed in the antenna pipe inside the waveguide in a direction of an axis of the gas flow pipe.
[claim2]
2. The plasma generator according to claim 1, wherein the slit has an opening formed on a side of the antenna pipe on which gas is discharged from the gas flow pipe.
[claim3]
3. The plasma generator according to claim 1, wherein the slit is formed as an opening in a body of the antenna pipe.
[claim4]
4. The plasma generator according to claim 1, wherein an edge of the slit has a portion which protrudes into an opening of the slit.
[claim5]
5. The plasma generator according to claim 1, wherein the antenna pipe is bent toward the gas flow pipe at an end on a side where gas is discharged from the gas flow pipe.
[claim6]
6. The plasma generator according to claim 1, wherein the length of the slit is set to more than 50 mm and less than 60 mm.
[claim7]
7. The plasma generator according to claim 1, comprising at least two of said slits, said slits being arranged around the gas flow pipe.
[claim8]
8. The plasma generator according to claim 1 , comprising a plurality of said gas flow pipes, wherein each gas flow pipe is surrounded by one of said antenna pipes.
[claim9]
9. A method for generating plasma using the plasma generator according to claim 1, comprising the steps of: a plasma igniting step, comprising keeping air pressure within the gas flow pipe lower than ambient pressure and igniting plasma through irradiation with microwaves; and
making the air pressure within the gas flow pipe the same as ambient pressure after the plasma igniting step.
[claim10]
10. The method for generating plasma according to claim 9, further comprising the step of, after making the air pressure within the gas flow pipe the same as ambient pressure, moving the gas flow pipe and the antenna pipe relative to each other so that an end portion of the gas flow pipe on a side where gas is discharged is closer to an end portion of the antenna pipe on a side where the slit is formed.
[claim11]
11. The method for generating plasma according to claim 10, wherein the microwaves with which the antenna pipe is irradiated are pulse driven, and an idle period of a pulse drive is within an average period during which plasma remains within the gas flow pipe.
[claim12]
12. The method for generating plasma according to claim 9, wherein the microwaves with which the antenna pipe is irradiated are pulse driven, and an idle period of a pulse drive is within an average period during which plasma remains within the gas flow pipe.
[claim13]
13. A method for generating plasma using the plasma generator according to claim 1, comprising the steps of: a first plasma igniting step, comprising supplying a first gas into the gas flow pipe and igniting plasma through irradiation with microwaves; and
supplying a second gas into the gas flow pipe, said second gas being more difficult to convert to plasma than the first gas, together with the first gas after the first plasma igniting step, and converting the second gas to plasma.
[claim14]
14. The method for generating plasma according to claim 13, further comprising the step of, after making the air pressure within the gas flow pipe the same as ambient pressure, moving the gas flow pipe and the antenna pipe relative to each other so that an end portion of the gas flow pipe on a side where gas is discharged is closer to an end portion of the antenna pipe on a side where the slit is formed.
[claim15]
15. The method for generating plasma according to claim 13, wherein the microwaves with which the antenna pipe is irradiated are pulse driven, and an idle period of a pulse drive is within an average period during which plasma remains within the gas flow pipe.
  • Inventor, and Inventor/Applicant
  • YONESU AKIRA
  • UNIVERSITY OF THE RYUKYUS
IPC(International Patent Classification)
U.S. Cl./(Sub)
  • H01J037/32M10
  • H05H001/24
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